5 speed tranny for 235?

[tool_zeppelin]

I'm builing my dad a truck and I'm trying to find a 5 speed transmission that can either bolt on or be adapted to fit a 235 inline 6 cyl. The truck is a hybrid 1950 and 1952 Chevy half ton with the best parts taken from each. He really wants to keep the 235 since he had a truck with the same engine when he was younger. I want to upgrade the tranny for him though and would appreciate any feedback on which tranny would work best. I'm also not against a solid 4 speed, just anything to ditch the 3 on the tree! Thanks.